Understand Chords: What's A Triad? (Part One of a Series)

Updated on April 19, 2015

Chords are a guitarist’s best friend—and a listener’s. Without “the chords” most modern melodies will sound bare and lifeless—but add them back, and sparkle and color return. Once again those melodies become the familiar friends we have come to know.

But what is a chord, exactly? Probably many people have an idea—a correct one!—that chords are groups of tones which belong together in some way. Those tones may be sounded simultaneously, as in a strummed guitar chord, or in sequence, as in traditional bugle calls like “Taps.” Either way, there will be some logic governing the choice of tones within a chord—a logic that lets our ears make sense of them.

The most common logic for chords is known as “tertian harmony,” and its basics are the topic of this Hub. I'll be using a lot of written-out musical examples, but they will include labels to help out--so if you don't really read music, you will still be able to follow the ideas.

To begin to understand tertian harmony we need to consider musical scales for a moment. In a scale, tones are arranged alphabetically by note name, as in the table below.

Guitar chord. Image courtesy Tom Gally & Wikimedia Commons. | Source

The note names of a specific scale are in the top row, arranged alphabetically—which also implies that they are arranged from lower to higher pitches. The second row indicates the position of the notes within the scale—this is often called their “scale degree.”

(Note the symbol for scale degree 8. That “a1” indicates another “a”--one sounding similar to, but “higher than,” the first scale degree. Musicians say it is an “octave” higher—“octave” from its position as the eighth note of the scale. A full discussion of all the implications and complications would be out of place here, but it’s helpful to know that all musical note names can occur in different octaves. So there are many “a”s, each of which sounds similar to, yet not identical with, all the others—and the same is true of all note names.)

Since the term “tertian” comes from a Latin root meaning “three,” it makes sense that “tertian harmony” would be formed by selecting tones “in thirds.” For example, if an “a” (scale degree 1) is sounded with a “c” (scale degree 3), these tones form the “interval of a third,” as shown in music notation below.

The notes "A" and "C" form a "third."

The same is true if a “c”
and an “e” sound together, as shown.

The third formed by "C" and "E."

And if all three tones
sound, the three form a structure you can think of as two thirds “stacked
together.”

"A," "C" and "E" form a complete triad--root, third and fifth.

This structure forms the characteristic ingredient of
tertian harmony: a three-note
chord called a “triad.” This
particular triad is named after its bottom tone, “a,” which is referred to as
the “root” of the triad; the other two chord members are referred to by their
relation to the root: they are the “third” and the “fifth” of the triad.

Note that a triad can be re-shuffled, so to
speak, so that it no longer appears to be composed of “stacked thirds,” and its
root is no longer appears to be literally the lowest tone. For example, the a minor triad might
have the fifth, “e,” sounding below the “a”:

A different "E," an "octave" lower than seen in the previous examples.

In this “voicing” the triad is less compact, and no longer
seems to consist of stacked thirds.
To the ear, it is subtly unstable.
Accordingly, the “stacked thirds” version is considered the normal
arrangement, and “a” remains the root, regardless of how the three chord
members are reshuffled.

The example below gives several possible
“reshufflings” or “revoicings” of our triad, but in each case there are only
three different notes present—a, c, and e—and in each case the arrangement we
first encountered in Example 3 represents its “ideal” structure. In each case, in other words, “a”
remains the root.

Different versions of our triad built on the root "A." Unfamiliar octave placements of chord tones are labeled.

By the way, this idea of triad roots answers a question some
beginning guitarists ask: why is
it that some chords use all six strings of the guitar, while others use only
five, or even four? In many cases
deeper strings are not included in the chord in order to play a “root position”
triad—one in which the lowest sounding tone actually is the root.

For example, the normal guitar voicing of our
example triad is given in the first of the two chords below. As can be seen, it includes only five
notes, the lowest of which is an “a.”
If a guitarist were to play the lowest string of the guitar as well, the
lowest note would then be “e,” not “a,” and the chord would be subtly less
stable-sounding. This voicing is
shown in the second chord of the example.

"Five-string" and "six-string" versions of our triad built upon "A." Version 2 is not in "root position," since "E," not "A," is the lowest-sounding note.

But there is more to triads than their different
positions. There is something
termed their “quality”—not as in “good” or “bad,” but rather like a
“flavor.” For example, if you take
the scale given above, it is possible to build triads using each successive
note of the scale as root. You
then have a series of seven different triads, as given in the example
below. Listen to them carefully,
and see if you can distinguish the different “flavors”—qualities—of each.

The seven triads in our scale.

Listen To Example 7

It’s not an easy task, because in addition to the different
qualities you have the difference in “flavor” resulting from the fact that each
triad is built on a different tone. Some listeners may hear seven different “flavors,” others may hear all
the triads as being basically the same. Yet others may hear two different qualities, with the second triad—the
one built upon the note “b”—sounding noticeably less pleasant than all the
others.

There is some validity to
all of these perceptions—but in the strict sense, there are actually three
different qualities of triad present in Example 7. Different qualities of triad result from different qualities
of thirds, and there are two basic qualities of third—traditionally, they are
called “major” and “minor.” We can
find thirds of both types within our familiar example triad.

To understand these major and minor thirds,
we can compare the positions of their notes upon the guitar fretboard or piano
keyboard. So we begin with “a” and
climb, one fret or piano key at a time, until we reach the “c” embodying the
third of the triad. We find that
we pass through two tones—b-flat and b—before we reach the “c,” for a total of
three “semitones.” (Each guitar
fret or piano key is a “semitone” away from its neighboring frets or keys.)

Doing the same thing
beginning from the “c” we find that we pass through three, not two,
tones—c-sharp, d, and e-flat—before reaching the e which is our goal. That’s four, not three, semitones. Logically, you would expect that three
semitones would make up the minor third, and four semitones would make up the
major. Thankfully, you would be
correct in this assumption.

Given these two types of thirds, we can theoretically
construct four different types of triads, as shown below:

But as it turns out, these
four types don’t occur on an equal footing in actual music. We can get a sense of this by figuring
out which qualities exist among the seven triads of Example 7. (If you’re really zealous about this,
grab a piece of scratch paper and your guitar or keyboard, and work it out for
yourself, using Example 7 as a starting point. It’s a great exercise, albeit somewhat tedious. You can check your results with Example
10 below—or you can just skip ahead, if you’re in a hurry.)

As shown, there are three minor triads—including our familiar a-c-e triad—and three major ones. There is only one diminished triad—the unstable-sounding one built upon “b,” mentioned above—and no augmented ones at all. In real music the distribution is even more unequal than this: overall, major triads appear more often that minor ones, though some songs might have more minor triads than major ones. Diminished triads are even less common than the one-out-of-seven proportion we just found, though they don’t really merit the term “rare” in most music. And augmented triads do occur in real musical life--but in most styles, “rare” probably is the appropriate term.

This set of observations accounts for a naming issue that I’ve dodged til now. It was remarked above that our a-c-e triad was (like all triads) named for its root, a. But that’s not its complete name; if one refers to an “a triad” or an “a chord,” that implies a major . "Our" triad, on the other hand, is correctly specified as “a minor.”

This naming convention makes sense, since major triads, the most common type, would naturally be expected to be the “default triad.” It's important to keep in mind, though, as too many folks tend to refer to any triad by the name of its root only. It's easy to do, but invites boatloads of confusion, so I discourage it. You could easily get something like this, for example:

So, let's recap just a bit. We've learned:

--"Tertian harmonies" are the most common, and comprise "triads" consisting of two "stacked thirds," three notes in all;

--Those three notes are termed "root, third and fifth;"

--In "default voicings" of triads, the root is the lowest sounding tone--this is called "root position"--but other arrangements than the "default" are possible, too;

--There are four types--"qualities"--of triads, which are defined by the arrangement of "minor" or "major" thirds within them;

--These types are called "diminished," "minor," "major" and "augmented;"

--In most styles of music, major triads are most common, followed closely by minor triads, then much more distantly by diminished, then augmented triads;

--In common terminology, a major triad can be specified by its root name only, but all other types require specifying the chord quality as well--for example, "c diminished."

That's quite a bit for one session, so let's leave further developments for another Hub!

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Comments 8 comments

A real hub and brilliantly written. Well laid out and explained. Thank you.

Doc Snow 6 years ago from Atlanta metropolitan area, GA, USA Author

Thanks so much, hello! It is always a pleasure to hear from you, and I'm so glad you have enjoyed this Hub.

6 String Veteran 5 years ago

Doc, you've covered a lot here, with patience and clarity. And then there are vid examples as well...a sizable effort, indeed, and well worth the read (no rhyme intended).

Btw, I've completed 3/3 posts on F Major, the last being dedicated to that dreaded bar on 1st Sreet...

Doc Snow 5 years ago from Atlanta metropolitan area, GA, USA Author

Thanks, 6SV! I saw your very detailed piece on the 'medium' F chord; it's good work. Feel free to put a link here, if you want to. I'll have to check out the other two as well!

Funnily enough, I was accompanying a buddy two nights ago on a cover of Cat Stevens' "Hard-headed Woman"--'funnily' because it has a couple of quick changes between Bb and F chords which can be a bit of a challenge. Actually, it's a good workout for barre chords, involving Gm and Cm as well.

DDS 5 years ago from Toronto

Oh I so don't get this stuff..which is maybe why I failed music in school.

Making music is fun though.

Doc Snow 5 years ago from Atlanta metropolitan area, GA, USA Author

Thanks, DDS! Sorry it confused you!

This is probably easiest when you actually work with someone in person, since you can ask questions before the confusion gets too bad.

This stuff isn't rocket science, but there are an awful lot of details to keep straight. Perhaps I packed too many into this Hub?

FatBoyThin 19 months ago from Kinneff, Scotland

I'm a pretty decent guitarist and I read music, but I've never been too hot on the theory of chords, so thanks for this, Doc - very helpful. Voted up.